Information recording medium

ABSTRACT

An information recording medium showing a high light-resistance has a recording layer containing a dye compound having the following formula (IV-2):                    
     in which each of Y 2  and Z 2  is a group of atoms required for forming a carbon ring or a heterocyclic ring; each of L 6 , L 7 , L 8 , L 9  and L 10  is a methine group which may have one or two substituents; M 2+  is an onium ion; and each of m1 and n1 is 0, 1 or 2.

FIELD OF THE INVENTION

This invention relates to an information recording medium on whichinformation can be recorded by means of a laser beam having a highenergy density, and a dye compound which is favorably utilized forpreparing the information recording medium.

BACKGROUND OF THE INVENTION

The recordable compact disc (CD-R), on which information can be recordedonly once, is widely used, for instance, as a large capacity computerdata disc.

The optical disc of CD-R type generally comprises a disc-shapedsubstrate (support) and a recording layer provided thereon. The discsubstrate comprises a transparent material such as synthetic resin. Therecording layer comprises a metal or a semi-metal such as Bi, Sn, In orTe, or alternatively a dye such as a cyanine dye, a metal-complex dye,or a quinone dye. A light-reflecting layer and a protective layer may besuperposed in order on the recording layer. The light-reflecting layerand the protective layer can be made of gold and resin, respectively.

On the CD-R, the writing (recording) and reading (reproducing) can beperformed in the following manner. The laser beam (usually usedwavelength is 780 nm) modulated by information is applied to therecording layer of the CD-R through the substrate. The recording layeralters its optical characteristics in the area where the laser beam hasbeen applied, to produce a chemical or physical change such asproduction of pit. The reading of the recorded information can beperformed by sequentially applying a laser beam on the recording layerof the CD-R through the substrate and detecting a light reflected on theCD-R.

At present, most of the recording layer of CD-R utilizes alight-sensitive dye as the recording material, because the recording dyelayer can be easily formed by a coating method and shows a highsensitivity, as compared with the recording metal layer. However, thedye layer has such disadvantages as low light-resistance and low heatresistance. Therefore, it has been desired to develop a recording layerhaving high durability against light and heat, as well as having highrecording and reproducing characteristics.

Japanese Patent Provisional Publication No. 63-209995 describes anoptical disc which has a recording layer comprising an oxonol dye.According to the description of publication, such optical disc maintainsstable recording and reproducing characteristics for a long time. Thepublication discloses an oxonol dye compound having an ammonium ion inthe form of an inner salt.

The inventors have found that the optical disc having the recordinglayer of the above oxonol dye exhibits insufficient light-resistance,while the disc has relatively improved characteristics in view of heatresistance and durability for repeated reproducing. Therefore, suchoptical disc often causes troubles in reproducing process after longexposure to light such as sunlight.

Accordingly, it is an object of the present invention to provide aninformation recording medium having stable recording characteristics andparticularly high light-resistance to maintain satisfactory recordingcharacteristics for a long time.

It is another object of the present invention to provide a new oxonoldye compound favorably employable for preparing the informationrecording medium having stable recording characteristics.

SUMMARY OF THE INVENTION

The present invention resides in an information recording mediumcomprising a support and a recording layer provided thereon on whichinformation can be recorded by means of a laser beam, wherein saidrecording layer contains a dye compound having the below-mentionedformula (I-1) or (I-2):

in which each of A¹, A², B¹ and B² independently represents asubstituent group; each of Y¹ and Z¹ independently represents a group ofatoms required for forming a carbon ring or a heterocyclic ring; each ofE and G independently represents a group of atoms required for forming aconjugated double bond chain; X¹ represents ═O, ═NR or ═C(CN)₂, whereinR is a substituent group; X² represents —O, —NR or —C(CN)₂, wherein R isa substituent-group; each of L¹, L², L³, L⁴ and L⁵ independentlyrepresents a methine group which may have a substituent group; M^(k+)represents an onium ion containing a positively charged onium atom towhich no hydrogen atom is attached; each of m and n independently is aninteger of 0, 1 or 2; each of x and y independently is an integer of 0or 1; and k is an integer of 1 to 10.

The invention further resides in a new oxonol compound having thebelow-mentioned formula (IV-1) or (IV-2):

in which each of A³, A⁴, B³ and B⁴ independently represents asubstituent group selected from the group consisting of a linear,branched or cyclic alkyl group having 1 to 18 carbon atoms, an alkenylgroup having 2 to 18 carbon atoms, an alkynyl group having 2 to 18carbon atoms, an aryl group having 6 to 18 carbon atoms, an aralkylgroup having 7 to 18 carbon atoms, an acyl group having 2 to 18 carbonatoms, an alkylsulfonyl group having 1 to 18 carbon atoms, anarylsulfonyl group having 6 to 18 carbon atoms, an alkylsulfinyl grouphaving 1 to 18 carbon atoms, an alkoxycarbonyl group having 2to 18carbon atoms, an aryloxycarbonyl group having 7 to 18 carbon atoms; analkoxy group having 1 to 18 carbon atoms, an aryloxy group having 6 to18 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, anarylthio group having 6 to 10 carbon atoms, an acyloxy group having 2 to18 carbon atoms, a sulfonyloxy group, a carbamoyloxy group, an aminogroup, a carbamoyl group, a sulfamoyl group, a halogen atom, a hydroxylgroup, a nitro group, a cyano group, a carboxyl group, and a 4- to7-membered heterocyclic group, wherein these substituent groups may besubstituted with at least one group selected from those consisting ofthe above-mentioned substituent groups;

each of Y² and Z² independently represents a group of atoms required forforming a 4- to 7-membered carbon ring or a 4- to 7-memberedheterocyclic ring, which may be substituted with at least one groupselected from those consisting of the substituent groups described forA³, A⁴, B³ and B⁴ and may be fused with a 4- to 7-membered carbon ringor a 4- to 7-membered heterocyclic ring;

each of L⁶, L⁷, L⁸, L⁹ and L¹⁰ independently represents a methine groupwhich may have one or two substituent groups selected from the groupconsisting of the substituent groups described for A³, A⁴, B³ and B⁴;

M²⁺ represents a quaternary ammonium ion; and

each of m1 and n1 independently represents an integer of 0, 1 or 2.

In contrast to the known oxonol dye compounds, the new oxonol dyecompound of the invention comprises an onium salt in which an onium atomhas no hydrogen atoms thereon (quaternary ammonium salt is particularlypreferred). The inventors have found that the new oxonol dye compoundenhances light-resistance to provide the information recording medium.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiments of the invention are as follows:

(1) M^(k+) in the formula (I-1) or (I-2) is a quaternary ammonium ion.

(2) k in the formula (I-1) or (I-2) is an integer of 0 to 4.

(3) k in the formula (I-1) or (I-2) is 2.

(4) M^(k+) is an onium ion of the below-mentioned formula (II):

in which each of R¹ and R² independently represents a group selectedfrom the group consisting of an alkyl group, an alkenyl group, analkynyl group, an aryl group or a heterocyclic group; each of R³ and R⁴independently represents a substituent group; or each set of R¹ and R³,R² and R⁴, or R³ and R⁴ can be combined to form a ring; each of q1 andr1 independently is an integer of 0 to 4; provided that plural R³ andplural R⁴ are the same as or different from each other in the case thatq1 and r1 are 2 or more, respectively.

(5) M^(k+) is an onium ion of the below-mentioned formula (III):

in which each of R⁵ and R⁶ independently represents a group selectedfrom the group consisting of an alkyl group, an alkenyl group, analkynyl group, an aryl group and a heterocyclic group; each of R⁷ and R⁸independently represents a substituent group; or each set of R⁵ and R⁶,R⁵ and R⁷, R⁶ and R⁸, or R⁷ and R⁸ can be combined to form a ring; eachof q2 and r2 independently is an integer of 0 to 4; provided that pluralR⁷ and plural R⁸ are the same as or different from each other in thecase that q2 and r2 are 2 or more, respectively.

(6) In the formula (I-1) or (I-2), each of m and n is 1; m is 0, while nis 2; or m is 2, while n is 2.

(7) In the formula (I-1) or (I-2), X¹ is ═O and X² is —O.

(8) A light-reflecting layer is provided on the recording layer.

(9) A protective layer is provided on the light-reflecting layer.

(10) M²+in the formula (IV-1) or (IV-2) is an ion having thebelow-mentioned formula (V):

in which each of R¹¹ and R¹² independently represents a group selectedfrom the group consisting of an alkyl group having 1 to 18 carbon atoms,an alkenyl group having 2 to 18 carbon atoms, an alkynyl group having 2to 18 carbon atoms, and an aryl group having 6 to 18 carbon atoms,wherein the alkyl, alkenyl, alkynyl and aryl group may be substitutedwith one or more groups selected from the group consisting of thesubstituent groups described for A³, A⁴, B³ and B⁴ of the formulas(IV-1) or (IV-2); each of R¹³ and R¹⁴ independently represents asubstituent group selected from the group consisting of the substituentgroups described for A³, A⁴, B³ and B⁴ of the formulas (IV-1) or (IV-2);or each set of R¹¹ and R¹³, R¹² and R¹⁴, or R¹³ and R¹⁴ can be combinedto form a 4- to 7-membered ring; each of q3 and r3 independently is aninteger of 0 to 4; provided that plural R¹³ and plural R¹⁴ are the sameas or different from each other in the case that q3 and r3 are 2or-more, respectively.

(11) M²⁺ in the formula (IV-1) or (IV-2) is an ion having thebelow-mentioned formula (VI):

in which each of R¹⁵ and R¹⁶ independently represents a group selectedfrom the group consisting of an alkyl group having 1 to 18 carbon atoms,an alkenyl group having 2 to 18 carbon atoms, an alkynyl group having 2to 18 carbon atoms, and an aryl group having 6 to 18 carbon atoms,wherein the alkyl, alkenyl, alkynyl and aryl group may be substitutedwith one or more groups selected from the group consisting of thesubstituent groups described for A³, A⁴, B³ and B⁴ of the formulas(IV-1) or (IV-2); each of R¹⁷ and R¹⁸ independently represents asubstituent group selected from the group consisting of the substituentgroups described for A³, A⁴, B³ and B⁴ of the formulas (IV-1) or (IV-2);or each set of R¹⁵ and R¹⁶, R¹⁵ and R¹⁷, R¹⁶ and R¹⁸, or R¹⁷ and R¹⁸ canbe combined to form a 4- to 7-membered ring; each of q4 and r4independently is an integer of 0 to 4; provided that plural R¹⁷ andplural R¹⁸ are the same as or different from each other in the case thatq4 and r4 are 2 or more, respectively.

(12) In the formula (IV-1) or (IV-2), each of m1 and n1 is 1; m1 is 0,while n1 is 2; or m1 is 2, while n1 is 0.

(13) In the formula (IV-1) or (IV-2), each of the carbon ring and theheterocyclic ring for the group of atoms represented by Y² or Z² ispyrazolone ring, ring of thiobarbituric acid, ring of barbituric acid,indandione ring, or hydroxyphenalenone ring.

The information recording medium of the invention and the new oxonolcompound are further described below.

The information recording medium of the invention is characterized bycomprising the recording layer containing the oxonol dye compound havingthe aforementioned formula (I-1) or (I-2).

The oxonol dye compound of the invention is described below in moredetail.

The oxonol dye compound favorably employable for the invention consistsessentially of an anion part (dye component) and a cation part (oniumcomponent).

First, the anion part is described.

Examples of the substituent groups represented by A¹, A², B¹ and B² inthe above formulas include following groups:

an alkyl group of 1-18 (preferably 1-8) carbon atoms which may have oneor more substituent groups and which may form straight-chain orbranched-chain or cyclic structure (e.g., methyl, ethyl, propyl,isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, cyclohexyl,methoxyethyl, ethoxycarbonylethyl, cyanoethyl, diethylaminoethyl,hydroxyethyl, chloroethyl, acetoxyethyl, and trifluoromethyl);

an aralkyl group of 7-18 (preferably 7-12) carbon atoms which may haveone or more substituent groups (e.g., benzyl, and carboxybenzyl);

an alkenyl group of 2-18 (preferably 2-8) carbon atoms (e.g., vinyl);

an alkynyl group of 2-18 (preferably 2-8) carbon atoms (e.g., ethynyl);

an aryl group of 6-18 (preferably 6-10) carbon atoms which may have oneor more substituent groups (e.g., phenyl, 4-methylphenyl,4-methoxyphenyl, 4-carboxyphenyl, and 3,5-dicarboxyphenyl);

an acyl group of 2-18 (preferably 2-8) carbon atoms which may have oneor more substituent groups (e.g., acetyl, propionyl, butanoyl, andchloroacetyl);

an alkylsulfonyl or arylsulfonyl group of 1-18 (preferably 1-8) carbonatoms which may have one or more substituent groups (e.g.,methanesulfonyl and p-toluenesulfonyl);

an alkylsulfinyl group of 1-18 (preferably 1-8) carbon atoms (e.g.,methanesulfinyl, ethanesulfinyl, and octanesulfinyl);

an alkoxycarbonyl group of 2-18 (preferably 2-8) carbon atoms (e.g.,methoxycarbonyl, and ethoxycarbonyl);

an aryloxycarbonyl group of 7-18 (preferably 7-12) carbon atoms (e.g.,phenoxycarbonyl, 4-methylphenoxycarbonyl, and 4-methoxyphenylcarbonyl);

an alkoxy group of 1-18 (preferably 1-8) carbon atoms which may have oneor more substituent groups (e.g., methoxy, ethoxy, b-butoxy, andmethoxyethoxy);

an aryloxy group of 6-18 (preferably 6-10) carbon atoms which may haveone or more substituent groups (e.g., phenoxy and 4-methoxyphenoxy);

an alkylthio group of 1-18 (preferably 1-8) carbon atoms (e.g.,methylthio and ethylthio);

an arylthio group of 6-10 carbon atoms (e.g., phenylthio);

an acyloxy group of 2-18 (preferably 2-8) carbon atoms which may haveone or more substituent groups (e.g., acetoxy, ethylcarbonyloxy,cyclohexylcarbonyloxy, benzoyloxy, and chloroacetyloxy);

a sulfonyloxy group of 1-18 (preferably 1-8) carbon atoms which may haveone or more substituent groups (e.g., methanesulfonyl);

a carbamoyloxy group of 2-18 (preferably 2-8) carbon atoms which mayhave one or more substituent groups (e.g., methylcarbamoyloxy anddiethylcarbamoyloxy);

an amino group having 0-18 (preferably 0-8) carbon atoms which may haveone or more substituent groups (e.g., non-substituted amino,methylamino, dimethylamino, diethylamino, anilino, methoxyphenylamino,chlorophenylamino, morpholino, piperidino, pyrrolidino, pyridylamino,methoxycarbonylamino, n-butoxycarbonylamino, phenoxycarbonylamino,methylcarbamoylamino, phenylcarbamoylamino, ethylthiocarbamoylamino,methylsufamoylamino, phenylsufamoylamino, acetylamino,ethylcarbonylamino, ethylthiocarbonylamino, cyclohexylcarbonylamino,benzoylamino, chloroacetylamino, methanesulfonylamino, andbenzenesulfonylamino);

a carbamoyl group of 1-18 (preferably 1-8) carbon atoms which may haveone or more substituent groups (e.g., non-substituted carbamoyl,methylcarbamoyl, ethylcarbamoyl, n-butylcarbamoyl, t-butylcarbamoyl,dimethylcarbamoyl, morpholinocarbamoyl, and pyrrolidinocarbamoyl);

a sulfamoyl group having 0-18 (preferably 0-8) carbon atoms which mayhave one or more substituent groups (e.g., non-substituted sulfamoyl,methylsulfamoyl, and phenylsulfamoyl);

a halogen atom (e.g., fluorine, chlorine, and bromine); hydroxyl group;nitro group; cyano group; carboxyl group; and

a heterocyclic group (oxazole, benzoxazole, thiazole, benzothiazole,imidazole, benzoimidazole, indolenine, pyridine, sulfolane, furan,thiophene, pyrazol, pyrrole, chroman, and coumarin).

Each of the substituent groups represented by A¹ and A² preferably hasHammett's substituent constant (σ_(p)) of not less than 0.2. The valuesof Hammett's substituent constant (σ_(p)) are set forth in, forinstance, Chem. Rev., 91, 165(1991). Examples of the particularlypreferred substituent groups include cyano group, nitro group,alkoxycabonyl group, acyl group, carbamoyl group, sulfamoyl group,alkylsufonyl group, and arylsulfonyl group. Examples of the preferredsubstituent groups represented by B¹ and B² include alkyl group, arylgroup, alkoxy group and amino group.

Each of the group of atoms [—C(═L¹)—(E)_(x)—C(═X¹)—] (hereinafterreferred to as “W1”) connecting to Y¹ and the group of atoms[—C(═L⁵)—(G)_(y)—C(═X²⁻)—] (hereinafter referred to as “W2”) connectingto Z¹ forms a conjugated system, and therefore each of the carbon ringor heterocyclic ring constituting W1 and Y¹ and that of W2 and Z¹ has aresonating structure.

Each of the carbon ring or heterocyclic ring of W1 and Y¹ and that of W2and Z¹ is preferably a 4- to 7-membered ring, more preferably a 5- or6-membered ring. Each ring may form a condensed-ring with other 4- to7-membered ring and may have substituent groups. Examples of thesubstituent groups are the same as those described hereinbefore for A¹,A², B¹ and B2. Examples of preferred hetero-atoms in the heterocyclicring include B, N, O, S, Se and Te. Among them, N, O and S areparticularly preferred.

Each of the numbers represented by x and y is independently 0 or 1, andpreferably both of them are 0.

X¹ is ═O, ═NR or ═C(CN)₂, and X² is —O, —NR or —C(CN)₂ in which R is asubstituent group. Examples of the substituent group R are the same asthose described hereinbefore for A¹, A², B¹ and B². Preferredsubstituent group R is an aryl group, and more preferably phenyl group.Preferred X¹ is ═O and preferred X² is —O.

Examples of the carbon ring constituting the set of W1 and Y¹ or the setof W2 and Z¹ include following rings (in which each of Ra and Rbindependently represents hydrogen atom or a substituent group):

Among the above rings, A-1 and A-2 are preferred.

Examples of the heterocyclic rings consisting of the set of W1 and Y¹ orthe set of W2 and Z¹ include following rings (in which each of Ra, Rband Rc independently represents hydrogen atom or a substituent group):

Among the above heterocyclic rings, A-5, A-6 and A-7 are preferred. Eachof Ra, Rb and Rc has the same meaning as that described hereinbefore forA¹, A², B¹ and B². Ra, Rb and Rc may be combined to from a saturated orunsaturated carbon ring (e.g., cyclohexyl ring, cyclopentyl ring,cyclohexene ring, and benzene ring), or a saturated or unsaturatedheterocyclic ring (e.g., piperidine ring, piperazine ring, morpholinoring, tetrahydrofuran ring, furan ring, thiophene ring, pyridine ring,and pyrazine ring). In that case, the ring may have one or moresubstituent groups. Examples of the substituent groups are the same asthose described hereinbefore for A¹, A², B¹ and B².

Each of L¹, L², L³, L⁴ and L⁵ independently represents a methine groupwhich may have one or more substituent groups. Examples of thesubstituent groups are the same as those described hereinbefore for A¹,A², B¹ and B². Among them, preferred substituent groups are an alkylgroup, an aralkyl group, an aryl group, alkoxy group, an aryloxy group,an alkylthio group, an arylthio group, a halogen atom, an amino group, acarbamoyl group and a heterocyclic group. The substituent groups may becombined to form a 5- to 7-membered ring (e.g., cyclopentene ring,1-dimethylaminocyclopentene ring, 1-diphenylaminocyclopentene ring,cyclohexene ring, 1-chlorocyclohexene ring, isophorone ring,1-morpholinocyclopentene ring and cycloheptene ring).

Preferred combinations of integers of m and n are m=1 and n=1; m=0 andn=2; and m=2 and n=0.

Next, the cation part is described in detail.

The onium ion represented by M^(k+) comprises an onium atom which haspositive charge and which has no hydrogen atoms thereon. Examples of theonium ions include a quaternary ammonium ion, oxonium ion, sulfoniumion, phosphonium ion, selenonium ion, and iodonium ion. Preferably,M^(k+) is not a cyanine dye but a quaternary ammonium ion.

A quaternary ammonium can be obtained by alkylation (Menshutkinreaction), alkenylation, alkynylation or arylation of a tertiary amine(e.g., trimethylamine., triethylamine, tributylamine, triethanolamine,N-methyl-pyrrolidine, N,N-dimethylpiperazine, triethylenediamine, andN,N,N′,N′-tetramethylethylenediamine) or a nitrogen-containingheterocyclic ring (pyridine, picoline, 2,2′-bipyridyl, 4,4′-bipyridyl,1,10-phenanthroline, quinoline, oxazole, thizole, N-methylimidazole,pyrazine, and tetrazole).

M^(k+) preferably is a quaternary ammonium ion comprising anitrogen-containing heterocyclic ring, and more preferably a quaternarypyridinium ion.

k is an integer of 1 to 10, preferably 1 to 4. More preferably, k is 2.

The most preferred onium ions for M^(k+) are ionic compounds having thebelow-mentioned formula (II) or (III):

in which each of R¹, R², R⁵ and R⁶ independently represents an alkylgroup, an alkenyl group, an alkynyl group, an aryl group or aheterocyclic group; each of R³, R⁴, R⁷ and R⁸ independently represents asubstituent group (including substituent atom); or each set of R³ andR⁴, R⁵ and R⁶, R⁷ and R⁸, R¹ and R³, R² and R⁴, R⁵ and R⁷ or R⁶ and R⁸can be combined to form a ring; each of q1, q2, r1 and r2 independentlyrepresents an integer of 0 to 4; under the condition that there can bedifferent R³, R⁴, R⁷ and R⁸ in the case that q1, q2, r1 and r2 are 2 ormore.

The above-mentioned onium ion for M^(k+) can be obtained by Menshutkinreaction (described in, for instance, Japanese Patent ProvisionalPublication 61-148162) or arylation (described in, for instance,Japanese Patent Provisional Publications 51-16675 and H1-96171) of2,2′-bipyridyl or 4,4′-bipyridyl with a halide having the desiredsubstituent.

The alkyl group preferably used for R¹, R², R⁵ and R⁶ is an alkyl groupof 1-18 carbon atoms which may have one or more substituent groups, andmore preferably an alkyl group of 1-8 carbon atoms which may have one ormore substituent groups. Examples of the alkyl groups include methyl,ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-hexyl, cyclohexyl andcyclopropyl.

Examples of substituent groups for the alkyl groups include:

a halogen atom (e.g., fluorine, chlorine, and bromine);

an alkoxy group of 1-18 (preferably 1-8) carbon atoms which may have oneor more substituent groups (e.g., methoxy and ethoxy);

an aryloxy group of 6-10 carbon atoms which may have one or moresubstituent groups (e.g., phenoxy and p-methoxyphenoxy);

an alkylthio group of 1-18 (preferably 1-8) carbon atoms which may haveone or more substituent groups (e.g., methylthio and ethylthio);

an arylthio group of 6-10 carbon atoms which may have one or moresubstituent groups (e.g., phenylthio);

an acyl group of 2-18 (preferably 2-8) carbon atoms which may have oneor more substituent groups (e.g., acetyl and propionyl);

an alkylsulfonyl or arylsulfonyl group of 1-18 (preferably 1-8) carbonatoms which may have one or more substituent groups (e.g.,methanesulfonyl and p-toluenesulfonyl);

an acyloxy group of 2-18 (preferably 2-8) carbon atoms which may haveone or more substituent groups (e.g., acetoxy and propionyloxy);

an alkoxycarbonyl group of 2-18 (preferably 2-8) carbon atoms which mayhave one or more substituent groups (e.g., methoxycarbonyl andethoxycarbonyl);

an alkenyl group of 2-18 (preferably 2-8) carbon atoms which may haveone or more substituent groups (e.g., vinyl);

an alkynyl group of 2-18 (preferably 2-8) carbon atoms which may haveone or more substituent groups (e.g., ethynyl);

an aryl group of 6-10 carbon atoms which may have one or moresubstituent groups (e.g., phenyl and naphthyl);

an aryloxycarbonyl group of 7-11 carbon atoms which may have one or moresubstituent groups (e.g., naphthoxycarbonyl);

an amino group having 0-18 (preferably 0-8) carbon atoms which may haveone or more substituent groups (e.g., un-substituted amino, methylamino,dimethylamino, diethylamino, anilino, methoxyphenylamino,chlorophenylamino, morpholino, piperidino, pyrrolidino, pyridylamino,methoxycarbonylamino, n-butoxycarbonylamino, phenoxycarbonylamino,methylcarbamoylamino, ethylthiocarbamoylamino, phenylcarbamoylamino,acetylamino, ethylcarbonylamino, ethylthiocarbonylamino,cyclohexylcarbonylamino, benzoylamino, chloroacetylamino, andmethylsulfonylamino);

a carbamoyl group of 1-18 (preferably 1-8) carbon atoms which may haveone or more substituent groups (e.g., non-substituted carbamoyl,methylcarbamoyl, ethylcarbamoyl, n-butylcarbamoyl, t-butylcarbamoyl,dimethylcarbamoyl, morpholinocarbamoyl, and pyrrolidinocarbamoyl);

a sulfamoyl group having 0-18 (preferably 0-8) carbon atoms which mayhave one or more substituent groups (e.g., non-substituted sulfamoyl,methylsulfamoyl, and phenylsulfamoyl);

cyano group; nitro group; carboxyl group; hydroxyl group; and

a heterocyclic group (e.g., oxazole, benzoxazole, thiazole,benzothiazole, imidazole, benzoimidazole, indolenine, pyridine,sulfolane, furan, thiophene, pyrazol, pyrrole, chroman, and coumarin).

The alkenyl group for R¹, R², R⁵ and R⁶ preferably is an alkenyl groupof 2-18 carbon atoms which may have one or more substituent groups, andmore preferably an alkenyl group of 2-8 carbon atoms which may have oneor more substituent groups. Examples of the alkenyl groups includevinyl, allyl, 1-propenyl and 1,3-butadienyl.

Examples of substituent groups for the alkenyl groups are the same asthose described hereinbefore for alkyl group.

The alkynyl group for R¹, R², R⁵ and R⁶ preferably is an alkynyl groupof 2-18 carbon atoms which may have one or more substituent groups, andmore preferably an alkynyl group of 2-8 carbon atoms which may have oneor more substituent groups. Examples of such alkynyl group includeethynyl and 2-propynyl.

Examples of substituent groups for the alkynyl groups are the same asthose described hereinbefore for alkyl group.

The aryl group for R¹, R², R⁵ and R⁶ preferably is an aryl group of 6-18carbon atoms which may have one or more substituent groups. Examples ofsuch aryl group include phenyl and naphthyl.

Examples of substituent groups for the aryl groups are the same as thosedescribed hereinbefore for alkyl group. Alkyl groups (e.g., methyl andethyl) are also preferably used as the substituent groups.

Examples of the heterocyclic groups preferably employable for R¹, R², R⁵and R⁶ include oxazole, benzoxazole, thiazole, benzothiazole, imidazole,benzoimidazole, indolenine, pyridine, sulfolane, furan, thiophene,pyrazol, pyrrole, chroman and coumarin.

Each of R³, R⁴, R⁷ and R⁸ has the same meaning as that describedhereinbefore for A¹, A², B¹ and B². Examples of the preferredsubstituent groups of R¹, R⁴, R⁷ and R⁸ include a hydrogen atom and analkyl group. Among them, a hydrogen atom is particularly preferred.

R⁵ and R⁶ are preferably combined to form a ring. In such case, the ringpreferably has 5 to 7 members, more preferably 6 members. Each of a setof R³ and R⁴ and a set of R⁷ and R⁸ is preferably combined to form acarbon ring or a heterocyclic ring, more preferably a carbon ring. It isparticularly preferred that each of the sets be combined with theconnected pyridine ring to form a condensed aromatic ring.

In the oxonol compounds of the formulas (IV-1) and (IV-2), A³, A⁴, B³and B⁴; Y² and Z²; L⁶, L⁷, L⁸, L⁹ and L¹⁰; and m1 and n1 have the samemeaning as those of A¹, A², B¹ and B²; Y¹ and Z¹; L¹, L², L³, L⁴ andL^(5;) and m and n in the formulas (IV-1) and (IV-2), respectively.Consequently, preferred examples of them are the same.

In M²⁺ of the formulas (V) and (VI), R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷and R¹⁸; and q3, r3, q4 and r4 have the same meaning as those of R¹, R²,R³, R⁴, R⁵, R⁶, R⁷ and R⁸; and q1, r1, q2 and r2 in the formulas (II)and (III), respectively. Consequently, preferred examples of them arethe same.

Concrete examples of preferred anion parts of the dye compounds of theformulas (I-1) and (I-2) are given below.

No. Ra Rb B-1 COOEt H B-2 COOEt CH₃ B-3 COOEt Ph B-4 COOEt CH₂CH₂OH B-5COOCH₃ Ph B-6 COOEt

B-7 COOEt CONHC₄H₉(n) B-8 COOEt CONHPh B-9 CN Ph B-10 COCH₃ Ph B-11 CF₃Ph B-12 CONHCH₃ CH₃ B-13 CONHCH₃ Ph B-14 CONHC₄H₉(n) Ph B-15 CONHPh PhB-16 CONHCH₃

No. Ra Rb L B-17 CONHC₄H₉(n) CONHC₄H₉(n) CH B-18 Ph H CH B-19 Ph CH₃ CHB-20 Ph Ph CH B-21 Ph

CH B-22

Ph CH B-23

Ph CH B-24

Ph CH B-25 Ph

C(CH₃) B-26 Ph CONHC₄H₉(n) CH B-27 Ph

CH B-28 COOEt CH₂Ph CH B-29 SO₂CH₃ Ph CH

No. Ra Rb L n B-30 CH₃SO₂NH Ph CH 1 B-31 HO Ph C(CONH₂) 1 B-32 CH₃ PhC(Ph) 1 B-33 CH₃ Ph C(CH₂Ph) 1 B-34 CH₃ Ph

1 B-35 EtO Ph CH 1 B-36 NHCOCH₃ Ph CH 1 B-37 NHCOPh Ph CH 1 B-38 NHCOPhCONHC₄H₉(n) CH 1 B-39 NHCOPh CONHPh CH 1 B-40 COOEt

CH 0 B-41 CN

CH 0 B-42 CF₃ Ph CH 0 B-43 CONHC₄H₉(n) Ph CH 0 B-44 NHCOC₄H₉(n) Ph CH 0

No. Ra Rb L B-45

CH B-46 NH₂ Ph CH B-47 NHCONHC₄H₉(n) Ph CH B-48 NHCOOC₄H₉(n) Ph CH B-49

CH₂Ph CH B-50 NHCOPh Ph C(Ph) B-51

Ph CH B-52

CH B-53 CN

CH B-54 CF₃

CH

No. Ra Rb L B-55 COOEt

C(CH₃) B-56 CN

C(CH₃) B-57 CF₃

C(CH₃) B-58 COCH₃

C(CH₃) B-59 COOEt

C(CH₃) B-60 CN

C(CH₃) B-61 COOEt

C(Br) B-62 COOEt

C(Cl) B-63 CN

C(Br)

No. Ra Rb L B-64 CN Ph C(Br) B-65 COOEt Ph C(Cl) B-66 COOEt Ph CH B-67CONHCH₃ Ph CH B-68 NHCOCH₃ Ph CH B-69 CH₃ Ph CH B-70 NH₂ Ph CH

No. Ra Rb X L B-71 H H O CH B-72 H CH₃ O CH B-73 H n-C₄H₉ O CH B-74n-C₄H₉ n-C₄H₉ O CH B-75 H Ph O CH B-76 H Ph O C(Ph) B-77 Ph Ph O CH B-78H

O CH B-79 H

O CH B-80 H H S CH B-81 H C₂H₅ S CH B-82 C₂H₅ C₂H₅ S CH B-83 H n-C₄H₉ OC(CH₂Ph) B-84 H Ph O C(CH₃) B-85 H Ph S CH

No. Ra Rb X L B-86 H n-C₄H₉ O CH B-87 H Ph O CH B-88 CH₃ CH₃ O CH B-89Ph Ph O CH B-90 H Ph O C(CH₃) B-91 H

O C(CH₂Ph) B-92 H n-C₄H₉ S CH B-93 H Ph S CH B-94 Ph Ph S CH B-95 Et EtS CH B-96 H Ph S C(CH₃) B-97

B-98

B-99

B-100

B-101

B-102

B-103

B-104

B-105

B-106

B-107 B-108

B-109 B-110

B-111

B-112

B-113

B-114

B-115

B-116

B-117

B-118

B-119

B-120

B-121

B-122

B-123

B-124

B-125

B-126

B-127 B-128

B-129 B-130

B-131

B-132

B-133

B-134

B-135

B-136

B-137

B-138

B-139

B-140

B-141

B-142

B-143

B-144

B-145

B-146

B-147

B-148

B-149

B-150

B-151

B-152

B-153

B-154

B-155

B-156

B-157

B-158 B-159

B-160

B-161

B-162

B-163

B-164

B-165

B-166

B-167

B-168

B-169

B-170

B-171

B-172

B-173

B-174

B-175

B-176

B-177

B-178

B-179

B-180

B-181

B-182

B-183

B-184

B-185

B-186

B-187

B-188

B-189

B-190

B-191

B-192

B-193

B-194

B-195

B-196

B-197

B-198

B-199

B-200

B-201

B-202

B-203

Concrete examples of preferred cation parts of the dye compounds of theformulas (I-1) and (I-2) are given below.

^(⊕)N(CH₃)₄ C-1 ^(⊕)N(C₂H₅)₄ C-2 ^(⊕)N(C₄H₉ ^((n)))₄ C-3

C-4

C-5 PhCH₂N^(⊕)(CH₃)₃ C-6 Ph—N^(⊕)CH₃)₃₇ C-7

C-8

C-9

C10

C-11

C-12

C13

C-14

C-15

C-16

No. R¹ R² C-17 CH₃ CH₃ C-18 C₂H₅ C₂H₅ C-19 n-C₃H₇ n-C₃H₇ C-20 n-C₄H₉n-C₄H₉ C-21 iso-C₄H₉ iso-C₄H₉ C-22 n-C₆H₁₃ n-C₆H₁₃ C-23 PhCH₂ PhCH₂ C-24CH₃—CH═CH—CH₂ CH₃—CH═CH—CH₂ C-25 CH₂═CH CH₂═CH C-26 NCCH₂ NCCH₂ C-27EtO₂C—CH₂ EtO₂C—CH₂ C-28 HOCH₂CH₂ HOCH₂CH₂ C-29 EtOCH₂CH₂ EtOCH₂CH₂ C-30CH₃ n-C₄H₉ C-31 CH₃ PhCH₂ C-32 CH₃COCH₂ CH₃COCH₂ C-33

C-34 CF₃CH₂ CF₃CH₂ C-35 Ph Ph C-36

C-37

C-38

C-39

C-40

C-41

C-42

C-43

C-44 [(C₄H₉)(CH₃)₂N—CH₂—CH₂—N(CH₃)₂(C₄H₉)]²⁺ C-45

C-46

C-47

C-48

C-49

C-50

C-51

C-52

C-53

C-54

C-55

C-56

C-57

C-58

C-59

C-60

C-61 Ph₃P^(⊕)Me C-62 C₁₆H₃₃ ^(⊕)P(C₂H₅)₃ C-63 Ph₄P^(⊕) C-64 (C₄H₉)₄P^(⊕)C-65 Ph—I^(⊕)—Ph C-66 Me₃S^(⊕) C-67

C-68

C-69

C-70

C-71

C-72

C-73

C-74

C-75

C-76

C-77

C-78

C-79

C-80

C-81

C-82

C-83

C-84

C-85

C-86

C-87

C-88

Concrete examples of the compounds preferably employable for theinvention are set forth in Table 1. In Table 1, each compound is shownas a combination of the anion part and the cation part. For example, thecompound of No. 1 (Compound No. 1) consists of-the anion part of (B-3)and the cation part of (C-1), and the compound of No. 5 (Compound No. 5)consists of the anion part of (B-3) and the cation part of (C-22).Consequently, each of the compounds of No. 1 and No. 5 has thebelow-mentioned formula:

The compounds in Table 1 can be illustrated in the same manner as thoseof No. 1 and No. 5 described above.

TABLE 1 Compound anion cation Compound anion cation No. 1 B-3 C-1 No. 11B-6 C-3 No. 2 B-3 C-3 No. 12 B-6 C-8 No. 3 B-3 C-8 No. 13 B-6 C-17 No. 4B-3 C-17 No. 14 B-6 C-22 No. 5 B-3 C-22 No. 15 B-6 C-41 No. 6 B-3 C-41No. 16 B-6 C-46 No. 7 B-3 C-46 No. 17 B-6 C-51 No. 8 B-3 C-51 No. 18 B-6C-53 No. 9 B-3 C-53 No. 19 B-9 C-51 No. 10 B-6 C-1 No. 20 B-11 C-51 No.21 B-20 C-1 No. 31 B-25 C-51 No. 22 B-20 C-3 No. 32 B-27 C-51 No. 23B-20 C-8 No. 33 B-40 C-1 No. 24 B-20 C-17 No. 34 B-40 C-8 No. 25 B-20C-22 No. 35 B-40 C-51 No. 26 B-20 C-41 No. 36 B-40 C-53 No. 27 B-20 C-46No. 37 B-41 C-20 No. 28 B-20 C-51 No. 38 B-41 C-51 No. 29 B-20 C-53 No.39 B-41 C-53 No. 30 B-21 C-51 No. 40 B-42 C-51 No. 41 B-53 C-3 No. 51B-64 C-51 No. 42 B-53 C-8 No. 52 B-71 C-1 No. 43 B-53 C-17 No. 53 B-71C-3 No. 44 B-53 C-22 No. 54 B-71 C-8 No. 45 B-53 C-51 No. 55 B-71 C-17No. 46 B-55 C-51 No. 56 B-71 C-22 No. 47 B-61 C-22 No. 57 B-71 C-41 No.48 B-61 C-51 No. 58 B-71 C-46 No. 49 B-61 C-53 No. 59 B-71 C-51 No. 50B-62 C-51 No. 60 B-71 C-53 No. 61 B-75 C-3 No. 71 B-82 C-51 No. 62 B-75C-8 No. 72 B-83 C-3 No. 63 B-75 C-35 No. 73 B-83 C-4 No. 64 B-75 C-51No. 74 B-83 C-8 No. 65 B-75 C-53 No. 75 B-83 C-21 No. 66 B-76 C-30 No.76 B-83 C-30 No. 67 B-76 C-51 No. 77 B-83 C-46 No. 68 B-78 C-1 No. 78B-83 C-51 No. 69 B-78 C-51 No. 79 B-83 C-58 No. 70 B-82 C-3 No. 80 B-87C-3 No. 81 B-87 C-30 No. 91 B-107 C-22 No. 82 B-87 C-51 No. 92 B-107C-41 No. 83 B-93 C-3 No. 93 B-107 C-46 No. 84 B-93 C-30 No. 94 B-107C-51 No. 85 B-93 C-51 No. 95 B-115 C-51 No. 86 B-97 C-51 No. 96 B-126C-51 No. 87 B-97 C-53 No. 97 B-134 C-51 No. 88 B-99 C-51 No. 98 B-138C-51 No. 89 B-99 C-53 No. 99 B-152 C-3 No. 90 B-107 C-3 No. 100 B-152C-51 No. 101 B-155 C-3 No. 111 B-162 C-74 No. 102 B-155 C-51 No. 112B-162 C-77 No. 103 B-161 C-3 No. 113 B-164 C-77 No. 104 B-161 C-51 No.114 B-166 C-76 No. 105 B-3 C-73 No. 115 B-167 C-77 No. 106 B-21 C-76 No.116 B-186 C-73 No. 107 B-82 C-74 No. 117 B-188 C-73 No. 108 B-82 C-84No. 118 B-192 C-77 No. 109 B-115 C-74 No. 119 B-196 C-77 No. 110 B-162C-22 No. 120 B-198 C-77 No. 121 B-199 C-77 No. 122 B-75 C-85 No. 123B-75 C-86 No. 124 B-75 C-87

The compound represented by the formula (I-1) or (I-2) can be easilyprepared by an ion-exchange reaction between the onium salt having thebelow-mentioned formula (VIII) and a salt of the dye compound having thebelow-mentioned formula (VII-1) or (VII-2). The dye compound can be usedin the form of an alkaline metal salt (e.g.; Li salt, Na salt, and Ksalt), an ammonium salt (NH₄ ⁺ salt) or a salt having an organic counterion such as a triethylammonium salt (Et₃NH⁺ salt) or a tributylammoniumsalt (Bu₃NH⁺ salt). The ion-exchange reaction can be carried out inwater or in an organic solvent (e.g., methanol, ethanol, isopropanol,and dimethylformamide).

In the above formulas, A⁵, A⁶, B⁵ and B⁶; Y³ and Z³; L¹¹, L¹², L¹³, L¹⁴and L¹⁵; X³ and X⁴; E1 and G1; m3 and n3; and x1 and y1 are the samemeaning as A¹, A², B¹ and B²; Y¹ and Z¹; L¹, L², L³, L⁴ and L⁵; X¹ andX²; E and G; m and n; and x and y in the formulas (I-1) and (I-2), andX^(r−) in the formula (VII) represents an anion, and r represents aninteger of not less than 1 (preferably 1 to 4, more preferably 1 or 2).Examples of the anions include halide ions (e.g., Cl⁻, Br^(—), and I⁻),sulfonato ions (CH₃SO₃ ⁻, p-toluenesulfonato ion, andnaphthalene-1,5-disulfonato ion), ClO₄ ⁻, BF₄ ⁻, and PF₆ ⁻.

The dye compound represented by the formula (VII-1) or (VII-2) can beprepared by a condensation reaction between the corresponding activemethylene compound (e.g., pyrazolone, thiobarbituric acid, barbituricacid, indandione, and hydroxyphenalenone) and the methine source tointroduce a methine group or polymethine group into the methine dye. Themethine source are described in detail in Japanese Patent PublicationNos. 39-22069, 43-3504, 52-38056, 54-38129, 55-10059, 58-35544; JapanesePatent Provisional Publication Nos. 49-99620, 52-92716, 59-16834,63-316853, 64-40827; British Patent No. 1133986; U.S. Pat. Nos.3,247,127, 4,042,397, 4,181,225, 5,213,956 and 5,260,179. Concreteexamples of the methine source for introducing of monomethine groupinclude ortho esters (e.g., ethyl orthoformate and ethyl orthoacetate)and N,N-diphenylformamidine hydrochloride. Examples of the methinesource for introducing of trimethine chain include trimethoxypropane,1,1,3,3-tetramethoxypropane and malonaldehydodianyl hydrochloride (andthe derivatives of those above described). Examples of the methinesource for introducing of pentamethine chain includeglutaconaldehydodianyl hydrochloride and1-(2,4-dinitrophenyl)-pyridiniumchloride (and the derivatives of thoseabove described).

The syntheses of the dye compounds represented by the formula (I-1) or(I-2) are described below.

SYNTHESIS EXAMPLES Synthesis Example 1

Synthesis of Compound No. 5

1 g of the compound (a) having the below-illustrated formula was addedto 20 ml of 0.1 N aqueous NaOH solution, and stirred at roomtemperature. Independently, 0.5 g of the compound (b) having thebelow-mentioned formula was dissolved in 5 ml of water. The preparedsolutions were mixed and stirred at room temperature for 30 minutes, andthen the formed precipitate was collected by filtration. The obtainedprecipitate was washed successively with water and ethanol, and thendried to give 0.23 g of the desired compound. λ_(max)=654 nm (inmethanol)

Synthesis Example 2

Synthesis of Compound No. 8

0.53 g of the above compound (a) was added to 10 ml of 0.1 N aqueousNaOH solution, and stirred at room temperature. Independently, 0.2 g ofthe compound (c) having the below-mentioned formula was dissolved in 5ml of water. The prepared solutions were mixed and stirred at roomtemperature for 30 minutes, and then the formed precipitate wascollected by filtration. The obtained precipitate was washedsuccessively with water and ethanol, and then dried to prepare 0.4 g ofthe desired compound. λ_(max)=654 nm (in methanol)

Synthesis Example 3

Synthesis of Compound No. 9

1 g of the above compound (a) was suspended in 20 ml of water. To theprepared suspension, 20 ml of 0.1 N aqueous NaOH solution was added andstirred at room temperature. Independently, 0.4 g of the compound (d)having the below-mentioned formula was dissolved in 5 ml of water. Theprepared liquids were mixed and stirred at room temperature for 30minutes, and then the formed precipitate was collected by filtration.The obtained precipitate was washed with water and ethanol, and thendried to prepare 0.2 g of the desired compound. λ_(max)=654 nm (inmethanol)

Synthesis Example 4

Synthesis of Compound No. 28

1 g of the compound (e) having the below-mentioned formula was added in10 ml of methanol. Into the prepared solution, 0.1 ml of 25 aqueous NH₃solution was dropped under stirring at room temperature. Independently,0.5 g of the above compound (c) was dissolved in 2 ml of water. Theprepared solutions were mixed and stirred at room temperature for 30minutes, and then the formed precipitate was collected by filtration.The obtained precipitate was washed with methanol, and then dried toprepare 0.8 g of the desired compound. λ_(max)=637 nm (in methanol)

Synthesis Example 5

Synthesis of Compound No. 67

0.55 g of the compound (f) having the below-mentioned formula wasdissolved in 10 ml of DMF. To the prepared solution, 0.17 g of the abovecompound (c) was added and stirred at room temperature for 1 hour, andthen 70 ml of water was added to form precipitate. The precipitate wascollected by filtration and washed with methanol, and then dried toprepare 0.5 g of the desired compound. λ_(max)=607 nm (in methanol):

Synthesis Example 6

Synthesis of Compound No. 71

0.93 g of the compound (g) having the below-mentioned formula was addedin 30 ml of methanol. Independently, 0.35 g of the above compound (c)was dissolved in 20 ml of methanol. The prepared solutions were mixedand stirred at room temperature for 150 minutes to form precipitate. Theprecipitate was collected by filtration and washed with methanol, andthen dried to prepare 0.9 g of the aimed compound. λ_(max)=633 nm (inmethanol)

Synthesis Example 7

Synthesis of Compound No. 86

1.0 g of the compound (h) having the below-mentioned formula was addedin methanol, and then 0.35 ml of triethylamine was further added. To thesolution, 0.46 g of the above compound (c) was added and stirred at roomtemperature for 60 minutes to form precipitate. The precipitate wascollected by filtration and washed with methanol, and then dried toprepare 0.85 g of the desired compound. λ_(max)=661 nm (in methanol)

Synthesis Example 8

Synthesis of Compound No. 89

1.1 g of the compound (i) having the below-mentioned formula was addedin 2.5 ml of 1 N aqueous NaOH solution. To the solution, 0.46 g of theabove compound (d) was added and stirred at room temperature for 60minutes to form precipitate. The precipitate was collected by filtrationand washed with methanol, and then dried to prepare 0.9 g of the desiredcompound. λ_(max)=652 nm (in methanol)

Synthesis Examples 9-11

Synthesis of Compounds Nos. 45, 46 and 98

Compounds Nos. 45, 46 and 98 were synthesized in the same manner as inthe Synthesis Example 2 or 4. The absorption spectrum of each preparedcompound in methanol was observed to find the absorption maximum(λ_(max)) as follows:

Compound No. 45: λ_(max) located at 654 nm;

Compound No. 46: λ_(max) located at 674 nm; and

Compound No. 98: λ_(max) located at 603 nm.

Synthesis Example 12

Synthesis of Compound No. 1

2.6 g of the above compound (a) was added in 50 ml of 0.1 N NaOH aqueoussolution. To the solution, 0.8 g of tetramethylammoniumbromide was addedand stirred at room temperature for 60 minutes to form precipitate. Theprecipitate was collected by filtration washed with water, and thendried to prepare 2.45 g of the desired compound. λ_(max)=654 nm (inmethanol).

Synthesis Examples 13-15

Synthesis of Compounds Nos. 3, 6 and 7

The procedure of Synthesis Example 12 was repeated except thattetramethylammonium bromide was replaced with each correspondingquaternary ammonium bromide, to synthesize each of Compounds Nos. 3, 6and 7. λ_(max)=654 nm (in methanol) for all

Synthesis Example 16

Synthesis of Compound No. 99

1.3 g of the compound (j) having the below-mentioned formula was addedin 10 ml of methanol. Into the prepared solution, 0.15 ml of 25% aqueousNH₃ solution was dropped under stirring at room temperature, and then1.4 g of tetrabutylammonium bromide was added and stirred at roomtemperature for 60 minutes to form precipitate. The precipitate wascollected by filtration and washed with methanol, and then dried toprepare 0.2 g of the desired compound. λ_(max)=671 nm (in methanol)

Synthesis Example 17

Synthesis of Compound No. 100

1.3 g of the above compound (j) was added in 10 ml of methanol. Into theprepared solution, 0.15 ml of 25% NH₃ aqueous solution was dropped understirring at room temperature. Independently, 0.38 g of the abovecompound (c) was dissolved in 20 ml of methanol. The prepared solutionswere mixed and stirred at room temperature for 120 minutes to formprecipitate. The precipitate was collected by filtration and washed withmethanol, and then dried to prepare 0.7 g of the desired compound.λ_(max)=671 nm (in methanol)

Synthesis Example 18

Synthesis of Compound No. 102

The procedure of Synthesis Example 17 was repeated except that thecompound (j) was replaced with 1.1 g of the compound (k) having thebelow-mentioned formula, to prepare 0.45 g of Compound No. 102.λ_(max)=655 nm (in methanol)

Synthesis Example 19

Synthesis of Compound No. 106

1.0 g of the compound (1) having the below-mentioned formula was addedin 10 ml of methanol, and then 0.2 ml of triethylamine was furtheradded. Independently, 0.3 g of the compound (m) having thebelow-mentioned formula was dissolved in 10 ml of methanol. The preparedsolutions were mixed and stirred at room temperature for 60 minutes toform precipitate. The precipitate was collected by filtration and washedwith methanol, and then dried to prepare 0.6 g of the desired compound.λ_(max)=636 nm (in methanol)

Synthesis Example 20

Synthesis of Compound No. 107

1.6 g of the aforementioned compound (g) was added in 20 ml of methanol,and then 0.5 ml of triethylamine was further added. Independently, 1 gof the compound (n) having the below-mentioned formula was dissolved in5 ml of methanol. The prepared solutions were mixed and stirred at roomtemperature for 60 minutes to form precipitate. The precipitate wascollected by filtration and washed with methanol, and then dried toprepare 1.6 g of the desired compound. λ_(max)=640 nm (in DMF).

Synthesis Example 21

Synthesis of Compound No. 109

2.5 g of the compound (o) having the below-mentioned formula was addedin 50 ml of DMF, and then 1 ml of triethylamine was further added.Independently, 1.5 g of the compound (n) was dissolved in 5 ml ofmethanol. The prepared solutions were mixed and then 50 ml of methanolwas dropwise added. The solution was stirred at room temperature for 60minutes to form precipitate. The precipitate was collected by filtrationand washed with methanol, and then dried to prepare 3 g of the desiredcompound. λ_(max)=707 nm (in methanol)

Synthesis Example 22

Synthesis of Compound No. 112

3.5 g of the compound (p) having the below-mentioned formula was addedin 50 ml of methanol, and then 1.5 ml of triethylamine was furtheradded. Independently, 2.5 g of the compound (q) having thebelow-mentioned formula was dissolved in 10 ml of methanol. The preparedsolutions were mixed to form precipitate. The precipitate was collectedby filtration and washed with methanol, and then dried to prepare 4.4 gof the desired compound. λ_(max)=661 nm (in DMF).

Synthesis Example 23

Synthesis of Compound No. 115

The procedure of Synthesis Example 22 was repeated except that thecompound (p) was replaced with 4.6 g of the compound (r) having thebelow-mentioned formula, to synthesize 2.3 g of Compound No. 115.λ_(max)=655 nm (in methanol)

Synthesis Example 24

Synthesis of Compound No. 116

0.3 g of the compound (s) having the following formula was added to themixed solvent of 5 ml of DMF and 15 ml of methanol, and then 1.2 ml oftributylamine was dropwise added under stirring. The resulting solutionwas further stirred for 30 minutes at room temperature, and then 0.3 gof the compound (t) having the below-mentioned formula was added. Thesolution was kept stirring for 2 hours to form precipitate. Theprecipitate was collected by filtration and washed with methanol, andthen dried to prepare 0.25 g of the desired compound. λ_(max)=606 nm (inDMF).

Synthesis Example 25

Synthesis of Compound No. 117

0.23 g of the compound (u) having the following formula was added inmethanol, and then 1.2 ml of tributylamine was further added. To theresulting solution, 0.28 g of the above compound (t) was added. Theresulting solution was stirred at room temperature for 60 minutes toform precipitate. The precipitate was collected by filtration and washedwith methanol, and then dried to prepare 0.22 g of the desired compound.λ_(max)=609 nm (in DMF).

Each of the compounds of the formula (I-1) or (I-2) of the invention canbe employed singly or in combination with two or more compounds.Further, a combination of plural compounds having the formula (I-1) anda combination of plural compounds having the formula (I-2) can be alsoemployed. Furthermore, the compound of the invention can be alsoemployed in combination with other known compounds.

The information recording medium of the invention has a recording layerprovided on a support, in which the recording layer contains the dyecompound represented by the formula (I-1) and/or (I-2). The informationrecording medium of the invention preferably has a light-reflectinglayer provided on the recording layer, and preferably has the mediumalso has a protective layer provided on the light-reflecting layer.

The information recording medium of the invention can be prepared by thefollowing method.

The substrate (support) which is transparent can be made of any ofmaterials known as the materials for the producing the substrate of thelight information recording medium. Examples of the materials includeglass, polycarbonate, acrylic resins such as polymethyl methacrylate,vinyl chloride resins such as polyvinyl chloride and vinyl chloridecopolymer, epoxy resins, amorphous polyolefins, and polyesters. Thesematerials can be employed in combination, if desired. These materialsare molded to give a film or a rigid plate. Most preferred is apolycarbonate resin from the viewpoints of anti-humidity and dimensionalstability.

The substrate may have on its surface on the recording layer side anundercoating layer for enhancing surface smoothness and adhesion, andkeeping the dye recording layer from deterioration. Examples of thematerial for the undercoating layer include polymers such as polymethylmethacrylate, acrylate-methacrylate copolymer, styrene-maleic anhydridecopolymer, polyvinyl alcohol, N-methylolacrylamide, styrene-vinyltoluenecopolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinylchloride, chlorinated polyolefin, polyester, polyimide, vinylacetate-vinyl chloride copolymer, ethylene-vinyl acetate copolymer,polyethylene, polypropylene, and polycarbonate, and surface treatingagents such as a silane-coupling agent.

The undercoating layer can be formed by coating a solution in which oneor more of the above-mentioned materials are dissolved or dispersed onthe surface of the substrate by the known coating methods such asspin-coat, dip-coat, and extrusion-coat. The undercoating layergenerally has a thickness of 0.005 to 20 μm, preferably 0.01 to 10 μm.

On the surface of the substrate or on the undercoating layer, groove fortracking or giving address signals is preferably formed. The groove ispreferably formed directly on the surface of the substrate when thesubstrate is molded from polymer material by injection or extrusion.

Alternatively, the groove can be provided on the surface of thesubstrate by placing a pregroove layer. The pregroove layer can beproduced from a mixture of a monomer such as monoester, diester,triester, or tetraester of acrylic acid, or its oligomer, and alight-polymerization reaction initiator. The pregroove layer can beproduced by the steps of coating a mixture of the polymerizationinitiator and the monomer such as the above-mentioned acrylic ester on aprecisely produced stamper, placing on the coated layer a substrate, andirradiating the coated layer with ultra-violet rays through the stamperor substrate, so as to cure the coated layer as well as to combine thecured layer and the substrate. The substrate to which the cured coatedlayer is attached is separated from the stamper, to give the desiredsubstrate equipped with the pregroove layer. The thickness of thepregroove layer generally is in the range of 0.05 to 100 μm, preferablyin the range of 0.1 to 50 μm.

The pregroove formed on the substrate preferably has a depth in therange of 300 to 2,000 angstroms and a half-width of 0.2 to 0.9 μm. Thedepth of 1,500 to 2,000 angstroms of the pregroove is preferably adoptedbecause such pregroove can enhance the sensitivity without decreasingthe light-reflection on the substrate. The optical disc having arecording layer (containing the dye compound of the formula (I-1) or(I-2)) coated on the deep pregoove and a light-reflection layer shows ahigh sensitivity, and hence is employable even in a recording systemusing a laser light of low laser power. This means that a semiconductorlaser of a low coat can be employed or the life of semiconductor lasercan be prolonged.

On the substrate, optionally via the undercoating, the recording layercontaining the above-described dye compound of the invention is placed.

In order to improve light-resistance, the recording layer may containvarious compounds known as singlet oxygen quencher. Examples of suchcompounds include a metal complex represented by the formula (III), (IV)or (V) of Japanese Patent Provisional Publication No. H3-224793;diimmonium salt; aminium salt; and nitroso compounds described inJapanese Patent Provisional Publications Nos. H2-300287 and H2-300288.

The recording layer can be formed on the substrate (support) by coatinga solution of a mixture of the dye of the invention, and if desired,quencher and binder in an organic solvent and drying the coated layer.Examples of the organic solvents include esters such as butyl acetateand cellosolve acetate; ketones such as methyl ethyl ketone,cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons suchas dichloromethane, 1,2-dichloroethane and chloroform; amides such asdimethylformamide; hydrocarbons such as cyclohexanone; ethers such astetrahydrofuran, diethyl ether and dioxane; alcohols such as ethanol,n-propanol, isopropanol, n-butanol, and diacetone alcohol;fluorine-containing solvents such as 2,2,3,3-tetrafluoropropanol; andglycol ethers such as ethyleneglycol monomethyl ether, ethyleneglycolmonoethyl ether, and propyleneglycol monomethyl ether. These solventscan be employed in combination, in consideration of the solubility ofthe used compound in the solvent.

The coating solution can further contain auxiliary additives such as anoxidation inhibitor, a UV absorber, a plasticizer, and a lubricant.

Examples of the binders include natural-origin polymers such as gelatin,cellulose derivatives, dextran, rosin, and rubber; hydrocarbon polymerresins such as polyethylene, polypropylene, polystyrene andpolyisobutyrene; vinyl polymers such as polyvinyl chloride,polyvinylidene chloride, and vinyl chloride-vinyl acetate copolymer;acrylate polymers such as polymethyl acrylate and polymethylmethacrylate; polyvinyl alcohol, chlorinated polyethylene; epoxy resins;butyral resins, rubber derivatives, and thermosetting resins such asprepolymers of phenol-formaldehyde. The binder is optionally employed inthe amount of 0.01 to 50 weight parts, preferably 0.1 to 5 weight parts,per 1 weight part of the dye.

The coating solution generally has a concentration of 0.01 to 10 weight% (solid content), preferably 0.1 to 5 weight %.

The coating can be performed by the known methods such as spray coat,spin coat, dip coat, roller coat, blade coat, doctor roller coat andscreen print.

The recording layer can be a single layer or can comprise plural layers.The thickness of the recording layer generally is in the range of 20 to500 nm, preferably 50 to 300 nm. The recording layer can be provided onboth of the surfaces of the substrate.

On the recording layer, the light-reflecting layer is placed so as toenhance the light-reflection in the course of reproduction ofinformation.

The light-reflecting material to be used for the formation of thelight-reflecting layer should show a high reflection to the laser light.Examples of the light-reflecting materials include metals and submetalssuch as Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni,Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po,Sn, and Bi. Stainless steel film is also employable. Preferredlight-reflecting material is Cr, Ni, Pt, Cu, Ag, Au and Al. Thesematerials can be employed singly or in the form of alloy.

The light-reflecting layer can be formed on the recording layer byvacuum deposition, sputtering or ion-plating. The thickness of thelight-reflecting layer generally is 10 to 200 nm, preferably 50 to 200nm.

On the light-reflecting layer can be placed a protective layer. Theprotective layer can be placed on the substrate on the side not havingthe recording layer.

The protective layer can be formed of inorganic materials such as SiO,SiO₂, MgF₂, SnO₂, Si₃N₄; or organic materials such as thermoplasticresins, thermo-setting resins, and UV curable resins.

The protective layer can be formed on the light-reflecting layer or thesubstrate by laminating a film of plastic material using an adhesive.The inorganic material can be placed on the light-reflecting layer orthe substrate by vacuum deposition or spattering. The organic polymermaterial can be coated in the form of a solution containing the polymermaterial and dried to give the protective layer. The UV curable resin isdissolved in a solvent and coated on the light-reflecting layer or thesubstrate, and cured by applying ultra-violet rays to the coated layer.The coating layer can contain various additives such as an anti-staticagent, an oxidation inhibitor, and a ultra-violet absorber. Theprotective layer generally has a thickness of 0.1 to 100 μm.

The information recording medium of the invention can comprise onesubstrate having one or two recording layers or two substrates each ofwhich has one recording layer and combined to give a known air sandwichstructure.

The information recording medium of the invention shows a highlight-reflection and an improved light-resistance as well as goodrecording and reproducing characteristics. Particularly, the informationrecording medium of the invention shows an extremely highlight-reflection of as high as 70%, and hence the reproduction of therecorded information can be accomplished by means of a commerciallyavailable CD player.

The information recording can be made in the following manner using therecording medium of the invention.

The information recording medium is rotated at a predetermined constantline rate (1.2 to 14 m/sec., in the case of CD format) or apredetermined constant angle rate. On the rotated medium, a recordinglight source such as a semiconductor laser beam is applied through thetransparent substrate. By the application of the laser beam, a pit isformed in the recording layer. The pit is assumed to be produced bylocal vacancy of the recording layer, deformation of the recording layerand/or the substrate, change of the physical or chemical characteristicsof the recording layer. The light source preferably is a semiconductorlayer having an oscillation frequency in the range of 500 to 850 nm. Thepreferred beam wave-length is in the range of 500 to 800 nm. In the caseof the CR-R type recording medium, the laser beam preferably has awavelength of 770 to 790 nm, while in the case of DVD-R type recordingmedium, the laser beam preferably has a wavelength of 630 to 680 nm.

The reproduction of the recorded information can be accomplished byapplying a semiconductor laser beam on the medium rotated at the samerate as that employed in the recording procedure. The light-reflectionis then detected on the substrate side.

The present invention is further described by the followingnon-restrictive working examples.

Example 1

3 g of the oxonol dye compound (Compound No. 1) of the invention wasdissolved in 100 ml of 2,2,3,3-tetrafluoropropanol to give a coatingsolution.

The coating solution was coated by spin coat on the surface of apolycarbonate substrate (diameter: 120 mm, thickness: 1.2 mm) to give acoated layer of approx. 200 nm thick. The substrate had a spirallyformed pregroove CL (track pitch: 1.7 μm, groove width: 0.4 μm, depth:0.16 μm) which was produced in the injection molding of the substrate.

On the coated dye layer was placed a light-reflecting layer of gold(thickness: approximately 100 nm) by sputtering, and then a UV curablephotopolymer (UV curable agent: SD-220, available from Dainippon Ink &Chemicals, Inc.) was coated to give a coated layer of 7 μm thick. Thecoated layer was irradiated with ultra-violet rays to be cured to form aprotective layer. Thus, an information recording disc according to theinvention was prepared.

Examples 2-15

The procedure of Example 1 was repeated except that the above oxonol dyecompound (Compound No. 1) was replaced with the same amount of each ofthe compounds set forth in Table 2, to prepare information recordingdiscs according to the invention.

Comparison Example 1

The procedure of Example 1 was repeated except that the above oxonol dyecompound (Compound No. 1) was replaced with the same amount of thefollowing cyanine dye compound (Compound A) having the cation part ofdye component and the anion part of perchlorate ion, to prepare aninformation recording disc for comparison.

Comparison Example 2

The procedure of Example 1 was repeated except that the above oxonol dyecompound (Compound No. 1) was replaced with the same amount of thefollowing oxonol dye compound (Compound B) having an ammonium saltsubstituted with three ethyl groups in the cation part, to prepare aninformation recording disc for comparison:

Comparison Example 3

The procedure of Example 1 was repeated except that the above oxonol dyecompound (Compound No. 1) was replaced with the same amount of thefollowing oxonol dye compound (Compound C) having an ammonium saltsubstituted with three ethyl groups in the cation part, to prepare aninformation recording disc for comparison.

Comparison Example 4

The procedure of Example 1 was repeated except that the above oxonol dyecompound (Compound No. 1) was replaced with the same amount of thefollowing oxonol dye compound (Compound D) having an ammonium-salt inthe cation part, to prepare an information recording disc forcomparison.

Comparison Example 5

The procedure of Example 1 was repeated except that the above oxonol dyecompound (Compound No. 1) was replaced with the same amount of thefollowing oxonol dye compound (Compound E) having an ammonium saltsubstituted with three ethyl groups in the cation part, to prepare aninformation recording disc for comparison.

[Evaluation of Information Recording Disc]

(1) Modulation

On the recording medium rotating at 1.4 m/sec., EFM signals of 3T and11T were recorded by means of a laser beam of wavelength 780 nm. Thelaser power was varied in the range of 4 mW and 9 mW. The recordedsignals were reproduced by the use of the laser beam having a laserpower of 0.5 mW. The modulation factors of the 3T and 11T signals weremeasured under the optimum power.

(2) Light-Reflection

The light-reflections of the pregroove (non-recorded area) were alsomeasured under the optimum power when the signals were reproduced.

(3) Light-Resistance

The recording medium was exposed to light from Xe lamp (140,000 lux) for18 hours or for 36 hours. Thereafter, the modulation factors andpregroove light-reflections were measured in the same manner describedabove. At the same time, the color of the recording medium was observedby sight to classify the degree of fading into the following ranks: AA:not faded, BB: slightly faded but acceptable, and CC: completely faded.

The results are set forth in the following Table 2.

TABLE 2 Oxonol Recording and Reproducing Characteristics Compound 3TMod. 11T Mod. Reflection Fading (Example 1) Compound No. 1 (none) 0.4020.701 72% — (18 hrs) 0.215 0.508 89% BB (36 hrs) — — — CC (Example 2)Compound No. 3 (none) 0.432 0.752 72% — (18 hrs) 0.253 0.520 88% BB (36hrs) — — — CC (Example 3) Compound No. 5 (none) 0.423 0.753 68% — (18hrs) 0.419 0.752 68% AA (36 hrs) 0.405 0.702 71% AA (Example 4) CompoundNo. 6 (none) 0.502 0.782 69% — (18 hrs) 0.495 0.752 69% AA (36 hrs)0.295 0.552 76% BB (Example 5) Compound No. 7 (none) 0.498 0.778 69% —(18 hrs) 0.485 0.723 70% AA (36 hrs) 0.263 0.532 79% BB (Example 6)Compound No. 8 (none) 0.572 0.823 67% — (18 hrs) 0.572 0.823 67% AA (36hrs) 0.571 0.821 67% AA (Example 7) Compound No. 9 (none) 0.512 0.76768% — (18 hrs) 0.511 0.766 68% AA (36 hrs) 0.510 0.765 68% AA (Example8) Compound No. 28 (none) 0.502 0.792 69% — (18 hrs) 0.502 0.791 69% AA(36 hrs) 0.501 0.790 69% AA (Example 9) Compound No. 45 (none) 0.5520.803 69% — (18 hrs) 0.552 0.803 69% AA (36 hrs) 0.551 0.802 69% AA(Example 10) Compound No. 46 (none) 0.531 0.782 68% — (18 hrs) 0.5300.782 68% AA (36 hrs) 0.528 0.781 69% AA (Example 11) Compound No. 67(none) 0.522 0.773 68% — (18 hrs) 0.520 0.772 69% AA (36 hrs) 0.5190.770 69% AA (Example 12) Compound No. 71 (none) 0.532 0.789 68% — (18hrs) 0.531 0.788 68% AA (36 hrs) 0.529 0.785 69% AA (Example 13)Compound No. 86 (none) 0.547 0.798 69% — (18 hrs) 0.546 0.797 69% AA (36hrs) 0.545 0.795 70% AA (Example 14) Compound No. 89 (none) 0.562 0.81370% — (18 hrs) 0.562 0.812 70% AA (36 hrs) 0.560 0.811 71% AA (Example15) Compoun.d No. 98 (none) 0.513 0.777 67% — (18 hrs) 0.502 0.722 69%AA (36 hrs) 0.415 0.542 73% AA (Example 16) Compound. No. 99 (none)0.502 0.745 70% — (18 hrs) 0.266 0.540 87% BB (36 hrs) — — — CC (Example17) Compound No. 100 (none) 0.522 0.767 70% — (18 hrs) 0.519 0.765 71%AA (36 hrs) 0.516 0.763 73% AA (Example 18) Compound No. 102 (none)0.512 0.753 72% — (18 hrs) 0.507 0.750 73% AA (36 hrs) 0.505 0.745 74%AA (Example 19) Compound No. 106 (none) 0.425 0.750 67% — (18 hrs) 0.4200.749 67% AA (36 hrs) 0.407 0.700 70% AA (Example 20) Compound No. 107(none) 0.530 0.786 68% — (18 hrs) 0.529 0.785 68% AA (36 hrs) 0.5260.781 69% AA (Example 21) Compound No. 109 (none) 0.498 0.779 68% — (18hrs) 0.497 0.778 68% AA (36 hrs) 0.495 0.777 69% AA (Example 22)Compound No. 112 (none) 0.512 0.767 70% — (18 hrs) 0.511 0.765 70% AA(36 hrs) 0.507 0.761 72% AA (Example 23) Compound No. 115 (none) 0.5020.743 70% — (18 hrs) 0.502 0.722 71% AA (36 hrs) 0.497 0.719 72% AA(Example 24) Compound No. 116 (none) 0.518 0.773 67% — (18 hrs) 0.5170.772 67% AA (36 hrs) 0.516 0.771 69% AA (Example 25) Compound No. 117(none) 0.513 0.777 67% — (18 hrs) 0.512 0.776 67% AA (36 hrs) 0.5100.774 68% AA (Example 26) Compound No. 119 (none) 0.470 0.763 69% — (18hrs) 0.469 0.762 69% AA (36 hrs) 0.465 0.759 71% AA (ComparisonExample 1) Compound A (none) 0.562 0.812 70% — (18 hrs) — — — CC (36hrs) — — — CC (Comparison Example 2) Compound B (none) 0.395 0.698 66% —(18 hrs) — — — CC (36 hrs) — — — CC (Comparison Example 3) Compound C(none) 0.265 0.552 65% — (18 hrs) — — — CC (36 hrs) — — — CC (ComparisonExample 4) Compound D (none) 0.355 0.652 65% — (18 hrs) — — — CC (36hrs) — — — CC (Comparison Example 5) Compound E (none) 0.402 0.708 67% —(18 hrs) — — — CC (36 hrs) — — — CC Remarks: (none) means the databefore exposure to Xe lamp, and (18 hrs) and (36 hrs) mean the dataafter 18 hours exposure and 36 hours exposure, respectively. “—” meansthat the tracking failed.

From the data set forth in Table 2, it is clear that each of the samples(Examples 1-18) of the invention (the information recording mediumhaving the recording layer containing oxonol compound comprising aquaternary ammonium ion) gives relatively stable modulation factors evenafter exposure to light from Xe lamp, and therefore they have highlight-resistance, as compared with the samples for comparison having therecording layer containing cyanine dye (Comparison Example 1), or oxonolcompound comprising tertiary ammonium salt (Comparison Examples 2, 3 and5) or ammonium salt (Comparison Example 4). In particular, the sampleshaving the recording layer containing oxonol compound comprisingdivalent cation part (Examples 3-15, Examples 17-18) exhibit remarkablyimproved light-resistance.

What is claimed is:
 1. An information recording medium comprising asupport and a recording layer provided thereon on which information canbe recorded by means of a laser beam; wherein said recording layercontains a dye compound having the following formula (IV-2):

in which each of Y² and Z² is independently selected from one of A-6,A-7, and A-12:

in which each of Ra and Rb independently represents a hydrogen atom or asubstituent group selected from the substituent groups consisting of alinear, branched or cyclic alkyl group having 1 to 18 carbon atoms, analkenyl group having 2 to 18 carbon atoms, an alkynyl group having 2 to18 carbon atoms, an aryl group having 6 to 18 carbon atoms, an aralkylgroup having 7 to 18 carbon atoms, an acyl group having 2 to 18 carbonatoms, an alkylsulfonyl group having 1 to 18 carbon atoms, anarylsulfonyl group having 6 to 18 carbon atoms, an alkylsulfinyl grouphaving 1 to 18 carbon atoms, an alkoxycarbonyl group having 2 to 18carbon atoms, an aryloxycarbonyl group having 7 to 18 carbon atoms, analkoxy group having 1 to 18 carbon atoms, an aryloxy group having 6 to18 carbon atoms, an alkylthio group having 1 to 18 carbon atoms, anarylthio group having 6 to 10 carbon atoms, an acyloxy group having 2 to18 carbon atoms, a sulfonyloxy group, a carbamoyloxy group, an aminogroup, a carbamoyl group, a sulfamoyl group, a halogen atom, a hydroxylgroup, a nitro group, a cyano group, a carboxyl group, and a 4- to7-membered heterocyclic group, wherein these groups may be substitutedwith at least one group selected from the above-mentioned substituentgroups; each of L⁶, L⁷, L⁸, L⁹ and L¹⁰ independently represents amethane group which may have one or two substituent groups selected fromthe substituent groups described for Ra and Rb of A-6, A-7, and A-12;M²⁺ represents an onium ion having the following formula (V) or (VI):

in which each of R¹¹ and R¹² independently represents a group selectedfrom the substituent groups consisting of an alkyl group having 1 to 18carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an alkynylgroup having 2 to 18 carbon atoms, and an aryl group having 6 to 18carbon atoms, wherein the alkyl, alkenyl, alkynyl and aryl groups may besubstituted with one or more groups selected from the substituent groupsdescribed for Ra and Rb of A-6, A-7, and A-12; each of R¹³ and R¹⁴independently represents a group selected from the substituent groupsdescribed above for Ra and Rb of A-6, A-7, and A-12; or each set of R¹¹and R¹³, R¹² and R¹⁴, or R¹³ and R¹⁴ can be combined to form a 4- to7-membered ring; each of q3 and r3 independently is an integer of 0 to4; or

in which each of R¹⁵ and R¹⁶ independently represents a group selectedfrom the substituent groups consisting of an alkyl group having 1 to 18carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an alkynylgroup having 2 to 18 carbon atoms, and an aryl group having 6 to 18carbon atoms, wherein the alkyl, alkenyl, alkynyl and aryl groups may besubstituted with one or more groups selected from the substituent groupsdescribed for Ra and Rb of A-6, A-7, and A-12; each of R¹⁷ and R¹⁸independently represents a group selected from the substituent groupsdescribed for Ra and Rb of A-6, A-7, and A-12; or each set of R¹⁵ andR¹⁶, R¹⁵ and R¹⁷, R¹⁶ and R¹⁸, or R¹⁷ and R¹⁸ can be combined to form a4- to 7-membered ring; each of q4 and r4 independently is an integer of0 to 4; and each of m1 and n1 independently represents an integer of 0,1 or
 2. 2. The information recording medium of claim 1, wherein alight-reflecting layer of metal or submetal is provided on the recordinglayer.
 3. The information recording medium of claim 1, wherein each ofm1 and n1 is 1; m1 is 0 while n1 is 2; or m1 is 2 while n1 is 0.